It's sensible to be afraid of sharks. The ancient predators have spent 400 million years honing their hunting skills, and some grow big enough to maul a human. It's also sensible, however, to keep the risks — and benefits — of sharks in perspective.
Sharks pose very little danger to people overall. Millions of us enter the ocean every year, yet the global average for unprovoked shark attacks is just 75, fewer than 10 of which are fatal. The odds of an attack are roughly one in 11 million, which pales in comparison to deadlier beach hazards such as boats, rip currents and lightning.
According to the International Shark Attack File (ISAF), a project of the American Elasmobranch Society and the Florida Museum of Natural History, sharks' treatment of their rare human victims suggests they don't see us as a delicacy. "The few attacks that occur every year are an excellent indication that sharks do not feed on humans," the ISAF explains, "and that most attacks are simply due to mistaken identity."
In fact, humans are far more dangerous to sharks than they are to us. We kill an estimated 100 million sharks every year, largely via fishing, finning and accidental bycatch. Along with other environmental upheaval like climate change and decline of prey species, this has raised widespread concern about the future of sharks, keystone predators that play vital ecological and economic roles around the world.
Our fear of sharks has been inflated by fiction, from old sailors' tales to modern movies that cast the fish as mindless monsters. Still, while we've gotten carried away in vilifying sharks, our original reasons for fearing them remain valid. And since our actions can influence whether sharks see us as prey, harboring a healthy fear might help us avoid needless risks without avoiding the ocean altogether.
"A shark attack is a human phenomenon," ISAF director George Burgess said in a recent statement. "Sharks are a natural part of the ecosystem. The ocean is a foreign environment to humans, and when we enter the sea, we're entering a wilderness."
Of more than 375 known shark species, only about 30 have ever been reported to attack a human. The species responsible for most unprovoked attacks are great whites, tiger sharks and bull sharks, although as the ISAF points out, all sharks are predators and "could be capable of inflicting wounds if provoked."
The risk of sharks varies widely by location, season and other factors, so there aren't many absolute rules that apply to every situation. But to discourage shark trouble in general, here are a few tips to keep in mind when you're in the ocean:
1. Don't provoke sharks.
A provoked shark attack is one instigated by a human touching a shark, whereas unprovoked means a shark made the first contact. Many provoked attacks occur in the context of fishing, such as unhooking sharks or removing them from nets, but Burgess writes that "recently there have been a number of incidents involving divers who were attacked after grabbing or feeding a shark while underwater."
It should go without saying, but trying to touch a wild shark is generally a bad idea.
2. Stick together.
Groups of people tend to be safer from sharks than lone surfers or swimmers. (Photo: Rosalba Tarazona/Flickr)
The ISAF has compiled a deep database of shark-attack records, covering more than 6,000 incidents from the 16th century through present day. Along with everything scientists know about shark behavior and biology, this offers some valuable insights into what can raise or lower the likelihood of a shark attack.
One of the simplest tips is a tactic used by many prey species at sea and on land, from anchovies to zebras: Find safety in numbers. "Sharks most often attack lone individuals," Burgess writes for the ISAF. Whether you're swimming, diving, surfing or just floating, your chances of a shark attack rise if you're isolated in the water.
On top of paying attention to how far you wander from your fellow beach-goers, the nonprofit conservation group Oceana also recommends staying within sight of a lifeguard "so help is nearby, should you need it."
3. Stay near shore.
This is good advice for multiple reasons. It's partly related to the tip above, since going too far from shore "isolates you and places you away from assistance," Burgess writes. But there's more to it than that, since sandbars, steep drop-offs and channel openings are popular hangouts for many prey species — and thus for sharks, too.
Plus, being in deeper water tilts the advantage even further toward sharks. Not only does it mean you're farther away from the safety of dry land; it also means you're in an environment where sharks can maneuver easily and you can't.
4. Stay dry after dark.
Night and twilight are nice times to be at the beach. It's typically cooler and less crowded, plus there's the beauty of a sunrise, sunset or Milky Way view over the ocean. These are not great times to go swimming in deeper water, however, because our affinity for night and twilight is shared by sharks (albeit for different reasons).
Burgess advises staying on land from dusk till dawn. "Many sharks are most active at these times," he writes, "and are better able to find you than you are to see them."
5. Don't bring bling.
Sharks may confuse shiny jewelry or colorful clothes with reflective scales of prey fish. (Photo: USFWS/Flickr)
Despite a persistent myth, sharks have pretty good vision. And thanks to a reflective layer in the eyes called the tapetum lucidum, they see better than we do in dark or murky water, and up to 10 times better in clear conditions. Still, this layer "defocuses light," Shark Savers explains, boosting visual sensitivity but reducing acuity.
Many shark "attacks" on humans are really more like investigations, in which a shark bites a person before it has really figured out what it's looking at, then leaves to find better food. Thankfully, sharks also have other keen senses to complement their vision (see below), so even these encounters are uncommon.
Still, if you're going into the ocean, it couldn't hurt to avoid clothes or accessories that might confuse sharks. Shiny jewelry or bedazzled swimsuits could attract unwanted attention, for example, because reflected light resembles the sheen of fish scales in certain conditions. Burgess also warns of swimming in brightly colored clothes, or with an uneven tan or sunburn, since "sharks see contrast particularly well."
Yet some swimwear is designed to get sharks' attention: By mimicking the colors of a venomous lionfish, it supposedly discourages sharks from seeing people as prey. There is science behind this, although some experts have expressed skepticism. Other products claim to repel sharks in different ways — like electricity, magnets or noise — although none can guarantee safety, and some have been tested more rigorously than others. For more details, check out this guide from Surfer Today.
6. Don't be bloody careless.
Blood can attract sharks, although they're pickier than many people think. (Photo: Nathan Wentworth/Flickr)
Sharks have many ways of finding prey, including organs called ampullae of Lorenzini that sense bioelectric fields. But perhaps their most famous superpower is their sense of smell, known for sniffing out tiny traces of blood in seawater. For maximum shark safety, the ISAF advises staying out of the ocean if you have a bleeding wound.
That is probably a good idea, but it's also worth noting that a little human blood — whether from a minor injury or menstruation — is unlikely to spark much interest from sharks. It won't lure them from miles away, despite a common myth, and even if a nearby shark does smell your blood, there's a good chance it won't bother you.
Sharks don't just blindly chase down every whiff of blood they smell; their senses are acute enough to detect specific amino acids of their natural prey. (The lemon shark, for example, can detect tuna oil at one part per 25 million.) And as shark expert Steve Kajiura told Vice in 2016, we flatter ourselves by assuming sharks want to eat us. "You can smell a landfill," Kajiura noted, "but it won't make you want to eat it."
7. Avoid fishy situations.
Human blood may not excite sharks, but it's a different story when their preferred prey bleeds. And even if sharks are drawn to an area by specific fish odors, certain species could also end up biting a human who got caught in the frenzy.
To prevent that kind of confusion, Burgess suggests avoiding waters where people are fishing, since accumulations of wild fish, bait fish and blood could attract sharks. Stay on land "especially if there are signs of bait fishes or feeding activity," he writes. "Diving seabirds are good indicators of such action." And beware waters polluted by sewage, Burgess adds, since that attracts bait fishes that tend to entice sharks.
8. Splash with care.
Splashing is typically harmless, but it could interest sharks in some situations. (Photo: Phuket@photographer.net/Flickr)
Even if you're far from crowds of fish, your behavior could still confuse a shark that happens to be nearby. Many sharks are instinctively intrigued by splashing, for example, which might lead them to injured prey. Of course, it's usually fine to splash at the beach, but it could be risky when combined with other risk factors, such as being in the ocean alone, at night, in shiny jewelry or in an area known for sharks.
Because the threat of sharks varies so from place to place and season to season, the ISAF's advice is just to "refrain from excess splashing," leaving it up to interpretation. Oceana also suggests staying vertical in deeper water, which it says "prevents you from looking like a seal and other larger prey." (There is some doubt about whether sharks really mistake us for seals, although research has shown visual similarities between surfers and seals when viewed from below.)
9. Don't be oblivious.
Humans are out of their element in the ocean, but we're also observant and adaptable enough to survive almost anywhere. Pay attention to official shark warnings, but also to your surroundings in the water. Even if you don't see a shark itself, you might notice subtler clues — fish that suddenly school together or dart away, for instance, could be reacting to the presence of a predator.
It's wise to be aware if you're in an area known for shark problems, too. A lack of recent incidents is no guarantee of safety, but since the statistics are available, we might as well take note of where most shark attacks tend to occur. The ISAF offers a world map of unprovoked shark attacks by country, but also zooms in for more detail in countries such as the United States, Australia, South Africa and Brazil. There are also county-level maps for U.S. states including Florida, Hawaii and California.
People who are bitten by a shark often never saw it coming, so if you do see a shark, it has already lost the valuable element of surprise. "Most sharks merely are curious and will leave on their own accord," according to the ISAF. "Enjoy your opportunity to see one of nature's most magnificent predators."
How to survive a shark attack
Shark attacks are extremely rare, but even if you take every precaution, entering the ocean always carries a small risk. So what should you do if a shark does bite you?
You'll probably already know if you've provoked the shark, but according to the ISAF, unprovoked shark attacks fall into one of three basic categories:
- Hit-and-run: In turbulent or murky water near shore, human movements at the surface sometimes look like fish to a shark. This can lead to the most common type of attack, in which a shark makes one bite, often on the legs or feet, before letting go and leaving. The human is usually left with minor injuries, rarely fatal.
- Sneak attacks: These encounters take place in deeper water, according to Burgess, and catch the victim by surprise. "The result can be serious injury or death," he writes, "especially if the shark continues to attack."
- Bump-and-bite: Sharks sometimes bump a person with their heady or body before circling back to bite, a type of encounter that can involve multiple attacks and thus has potential for serious injury or death.
If a possibly dangerous shark is spotted, the best response depends on context. Near the beach, you should probably head for shore. When you're diving or in deep water, the ISAF advises staying calm and quietly holding your position. If the shark is too interested and swims at you, the recommended strategy is to move away — swimming "quickly but smoothly" and keeping your eyes on the shark.
For more dire situations, use whatever object you can find as a weapon. The best tactic for stopping a shark attack is to hit the shark on the tip of its snout, according to the ISAF, which usually causes the shark to retreat. If that works, you should retreat, too, before the shark changes its mind and returns. Subsequent hits to the nose may be less effective, so don't waste an opportunity to escape.
If a shark bites onto you, the ISAF suggests being as aggressively defensive as possible. Unlike with a grizzly bear, playing dead doesn't work with sharks. They do sometimes abandon feisty prey, so try to claw at sensitive areas, namely the eyes and gill openings, and flee as soon as the shark lets go. There is no universal trick to surviving a shark attack, though, so Burgess recommends listening to your instincts.
"If attacked by a shark, the general rule is 'Do whatever it takes to get away!'" Burgess writes. "Some people have successfully chosen to be aggressive, others passive. Some yelled underwater, others blew bubbles."
"I personally would go down fighting," he adds.